Methods for the image-wise exposure of a moving light-sensitive medium by means of a light source and a plurality of switchable light valves disposed between the medium and the light source are well known. Generally, a light source and a number of switchable light valves disposed between the light source and the light-sensitive medium are connected to an actuating system controllable by image data. A synchronization device is connected to the actuating system for delivering a synchronization signal in accordance with the movement of the light-sensitive medium.
Illustrative of this type of device, is U.S. Pat. No. 4,375,648, in which image formation takes place by means of a two-dimensional array of light valves disposed at a small angle to the direction of advance of a light-sensitive layer and just above the latter. Each light valve is provided with a lens so that it is possible to image a relatively large light valve as a relatively small image dot. The small angular rotation of the array causes the image dots imaged on a reduced scale to be situated exactly next to one another as considered in the direction of movement of the light-sensitive layer.
A disadvantage of this type of device is that for the image-wise exposure of one line the image signals for each light valve in the array must have a specific delay time so that a complex control circuit is required. A two-dimensional lens array made and positioned with great accuracy is also required. Accordingly, it is an object of the invention is to obviate these and other disadvantages.